Hey all, My wife and I just recently (2 weeks ago) bought a 98 accord 150k and we test drove it and everything, it was a really strong car. I know a little about cars, so I felt confident in buying it.

4 days later the Check engine light came on. The car runs completely fine and everything, the only difference in the whole car is my brake light in the back is out. Nothing changed when it came on. I took it to AAMCO and they said it was my ECM, 1,000 to fix. I don't understand how the car can still run fine if the ECM is bad, plus the guy didn't seem to knowledgable about what he was doing either. The Code that came up said Fuel/air mix. Has anyone come accross this, does anyone know someone who is in the Stockton area that's reputable?

I'll find the exact code and post it on here. I just don't understand how the ECM can be out and the car run fine.

I have the exact same problem with my exact same '98 Honda Accord. It could either be the sensor, or have you filled up the gas tank lately? If you don't turn the gas cap enough the check engine light will come on. This happens all the time with mine. I make sure that every time I fill up I tighten through several "clicks" of the gas cap. It usually takes about 50 miles of driving for the check engine light to reset itself.

You can also try disconnecting the battery to reset the computer; however, you will need the 6 digit code to enter into the radio. IMO... AAMCO is trying to rip you off.

'98 means that it is OBDII, so tt is easy to pull the specific code(s).

Gas cap usually throws an evap system code. fuel/air mix is likely O2 sensor, cat, and/or fuel delivery (injectors, fuel pump, fuel filter, etc. altering desired ratio). Go to AutoZone or equivalent and get the actual MIL code, then look it up in a Honda forum (or post it here). An immediate jump to changing computer is a little silly, especially on a Honda.

I would guess this is not a new issue, and that the seller just cleared the CEL for test drive purposes. The fact that it took a few miles to throw a code pretty much confirms any suspicion along those lines (although it could very well be coincidence).

Also, you should find a new mechanic as I suspect he is asking you, in his own language, to grab your ankles.

Most delayed CELs that require a few diving cycles to trip are emissions related, especially if you do not notice any issues with drivability, smoke, etc.

You can certainly clear codes easily by disconnecting the juice (although just the negative (black cable) will do the job) for a short time. Press the brake pedal or turn on the lights to bleed any juice faster.

I really recommend pulling the code(s) before clearing it. It is free, and could catch a bigger problem like misfire, etc. Confidence in what this super mechanic says should be low.

Called Honda dealer and said that AAMCO told me my ECM was going out. The guy at Honda told me that this happens and that it would be 1,500 to change it. The problem I dont have 1,500 to spend. There is an option on the Honda website that they can do a "goodwill" servie and fix ti for free but the assistant manager said that that typically was for cars 5 to 6 years old, not older. Going to call the manager today.

Im gonna try and make extra sure the gas cap is tight.

If I disconnect the power, and clear the code, is there any harm that could come from that or not?

I do think the owner cleared the code it was about 70 miles after owning it that the light came on.

The P code is a manufacturers code and will not show up with a generic scan tool. There will not be anything in Mode $0A either as it is too old of a vehicle. Before clearing any code one should always check both sides of the computer especially the pending codes.

What are the long term fuel trims? This requires a scanner hooked up to know and will tell a lot about how the stoichiometric is doing. If you have a super fast non averaging DSO with a min/max you could at least get an idea if it is switching.

"Most likely" it is just a bad air fuel ratio sensor. It can effect the cat although it is probably failing at that mileage anyhow. It will effect fuel economy if the sensor is failing. You can check Rock Auto dot com to see how much one is.

Primary O2 sensors for most hondas are $50-60 for the OEM fit. Secondary should be similar if not less (I usually change both at the same time). It is a really easy fix.

It does look like Honda had issues with ULEV/SULEV ECMs being overly touchy. Looks like they are not "breaking" but just touchy from the start. New O2 sensors alone still might do the trick though.

As far as ~70 miles driven, that seems about right for a tripped emmisions CEL.

My bet is that LTFT is not going to mean much in this case as I am willing to bet the codes were cleared in order to sell the car (and likewise the LTFT). It would be more interesting to see what ECU tests are "not ready" pending additional miles/drive cycles.

As far as the P code being a manufacturers code, I agree, but not sure what you mean about not showing up with a scan tool?? The description may be off, but the code should be accurate . . . .

That is NOT an O2 sensor it is an air fuel ratio sensor aka wide band O2. If it is a 2.3L motor the sensor is $137. from Rock Auto Parts. Be careful pulling them out. Sometimes a torch is the best way to preserve the bung. Often times it takes a special socket but it has been a long time since I looked at a '98 Honda so I have no idea if a wrench will work or not. Sockets are pretty cheap.

The LT fuel trims start recoding immediately and can tell a story 15 minutes after started. The readiness monitors are a good thing to check I will agree with that, but how many people have a scanner available to access Mode $05 and Mode $06 to do so? Really both are useless to the OP at this point.

FWIW manufacturer codes generally do not show up on a generic scan tool in Mode $03. Mode $02 the freeze frame data, tells the story of who, what, where, when. They will show up on a scanner that can access the manufacturers side of the computer though.

What would I do if I didn't have test equipment available? Throw a $137 sensor in and hope it fixes it. Cheaper than spending the $100 to have someone test it to find out it is a sensor. Heck half the people read the codes and buy the parts, which nails it about 80% of the time. Hopefully yours is not in the 20%.

good consideration is usually for original owners who spend money at the dealer to have regular maintenance done. At least those were the paramaters when I worked in teh service department of a ford dealer. As you already know, it's basically for car's that are "just out of warranty".